A new study reported by ScienceDaily suggests coffee may affect the brain through the gut.
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coffee → report → gut
Researchers at APC Microbiome Ireland and University College Cork discovered that both caffeinated and decaffeinated coffee were associated with alterations in gut microbes and metabolites linked to mood, stress and cognitive function.
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coffee → discover → mood
Those who resumed coffee drinking after a two-week break reported lower levels of perceived stress, depression and impulsivity.
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who → resume → stress
The findings, published in
Nature Communications, also showed differences between regular and decaffeinated coffee, with decaf associated with better learning and memory, and caffeinated coffee with less anxiety and better attention.
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decaf → publish → anxiety
However, the study was small and does not prove that coffee directly improves mental health.
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coffee → prove → health
Looking beyond caffeine
Coffee is often viewed as a quick way to feel more awake, particularly at the start of a demanding day.
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Coffee → look → day
Its effects, however, may extend well beyond alertness.
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effects → extend → alertness
Coffee contains caffeine, but it also includes polyphenols, phenolic acids and other plant compounds that can interact with the body’s metabolism and the microorganisms living in the digestive system.
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that → contain → system
The study explored the microbiota-gut-brain axis, the two-way communication network connecting the gut and the brain.
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study → explore → gut
Signals can travel between these systems through the immune system, hormones, nerves and chemicals produced when gut microbes process food and drinks.
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microbes → travel → food
That suggests changes in the gut microbiome could affect mood, stress responses and parts of cognition, although scientists are still working out how exactly it does so.
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it → suggest → cognition
To study this connection, researchers studied 31 habitual coffee drinkers and 31 people who didn’t regularly drink coffee.
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who → study → coffee
They first stopped drinking coffee for two weeks, allowing researchers to observe what changed when coffee was removed from their routines.
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coffee → stop → routines
Coffee was then added back for 21 days, with participants receiving either caffeinated or decaffeinated coffee without knowing which type they were drinking, as per the report.
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they → add → report
Mood changes after coffee returned
When coffee was reintroduced, both groups reported lower scores for perceived stress, depression and impulsivity.
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groups → return → stress
This was one of the most significant findings because it suggests that some of coffee’s possible effects on mood may not depend entirely on caffeine.
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some → suggest → caffeine
If caffeine were responsible for every change, researchers would not necessarily expect decaffeinated coffee to show similar associations.
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coffee → expect → associations
The findings also suggested that regular and decaffeinated coffee may have different effects on people.
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coffee → suggest → people
Those who drank caffeinated coffee reported feeling less anxious and less psychologically distressed.
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who → drink → coffee
Caffeinated coffee has also been linked to greater vigilance and attention.
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coffee → link → vigilance
Decaffeinated coffee, meanwhile, was linked to improvements in learning and episodic memory, as well as better sleep quality and increased physical activity.
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coffee → link → learning
These findings should be taken with caution.
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findings → take → caution
The study involved a small number of people and the participants were healthy adults.
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participants → involve → people
Also, some memory improvements could have been affected by better sleep, more physical activity or familiarity with the tests.
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improvements → affect → tests
The researchers also relied partly on questionnaires, which measure how participants felt and behaved but cannot capture every aspect of mental health.
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participants → rely → health
Gut bacteria react to coffee
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bacteria → react → coffee
The researchers found that coffee drinking was associated with changes in some gut bacteria, including Eggertella species and Cryptobacterium curtum.
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drinking → find → species
They also noticed changes in members of the Firmicutes group.”
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They → notice → group
Instead, coffee appeared to influence particular strains within the gut community.
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coffee → appear → community
The study also identified changes in metabolites, which are small molecules made or changed in the course of metabolism.
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which → identify → metabolism
Some of the compounds seemed to be coming directly from coffee itself, while others were linked to the activity of gut microbes.
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others → seem → microbes
Caffeine-related chemicals appeared in the caffeinated coffee group, but several coffee-related phenolic compounds changed after both caffeinated and decaffeinated coffee were consumed.
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coffee → relate → group
This may help explain why decaf appeared to have effects of its own.
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decaf → help → own
Coffee’s non-caffeine compounds can be processed by gut bacteria, and the resulting metabolites may influence biological pathways involved in inflammation, mood and brain function.
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metabolites → process → inflammation
The researchers found statistical links between certain microbial species, metabolites and cognitive or behavioural measures, but these links do not yet establish a direct cause.
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links → find → cause
What the study does not prove
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prove → prove → What
The findings do not mean that coffee can prevent depression, treat anxiety or replace professional mental health care.
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coffee → mean → care
They also do not suggest that everyone should begin drinking several cups of coffee each day.
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everyone → suggest → coffee
A person’s response to coffee can depend on genetics, sleep, diet, medication, caffeine sensitivity and existing medical conditions.
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response → depend → genetics
Too much caffeine may cause restlessness, digestive discomfort, a racing heartbeat or difficulty sleeping.
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caffeine → cause → restlessness
…and 9 more, not listed.
The Aporia
